在以兩列為條件的行序列上過濾 dataframe

Question

我有這種類型的數據，其中Sequ列中的數值定義了一系列行，而Q中的字符值命名了序列的類型：

df <- data.frame(
  Line = 1:12,
  Speaker = c(NA, "ID01.A", NA, "ID01.B", "ID07.A", NA, "ID33.B", 
              "ID33.A", "ID33.C", NA, "ID77.A", "ID77.C"),
  Utterance = c(NA, "Who did it?", "(1.99)", "Peter did.", "Hello!", NA, "So you're coming?", 
                "erm", "Yes, sure.", "(0.22)", "Good night?", "Yeah, sleep well"),
  Sequ = c(NA,1,1,1, NA,NA, 2,2,2, NA, 3,3),
  Q = c(NA, "q_wh", "", "", NA, NA, "q_decl", "", "", NA, "q_wh", "")
)

我想將 dataframe 子集化為數字（而不是NA ）和其中Q == q_wh的那些Sequ值。 我可以使用na_if然后fill來完成此任務：

library(tidyr)
df %>%
  mutate(Q = na_if(Q, "")) %>%
  fill(Q, .direction = "down") %>%
  filter(!is.na(Sequ) & Q == "q_wh")
  Line Speaker        Utterance Sequ    Q
1    2  ID01.A      Who did it?    1 q_wh
2    3    <NA>           (1.99)    1 q_wh
3    4  ID01.B       Peter did.    1 q_wh
4   11  ID77.A      Good night?    3 q_wh
5   12  ID77.C Yeah, sleep well    3 q_wh

但是，是否有另一種更直接的方法，無需繞過na_if和fill來過濾df ？

Answer 1

只需使用條件進行子集化。

df[with(df, !is.na(Sequ) & Q == 'q_wh'), ]
#    Line Speaker   Utterance Sequ    Q
# 2     2  ID01.A Who did it?    1 q_wh
# 11   11  ID77.A Good night?    3 q_wh